The present invention relates to a leaf spring assembly for wheel suspensions, and more particularly to a leaf spring assembly of the type which comprises a longitudinal leaf spring of fiber reinforced plastics, a pair of retainer plates attached to opposite surfaces of the leaf spring, and a pair of fastening U-bolts and nuts for clamping the retainer plates to the leaf spring and mounting the same on an axle housing.
In such a conventional leaf spring assembly as described above, it required a mechanism to facilitate positioning of the leaf spring at its central portion during mounting process of the leaf spring assembly. For such requirement, as is illustrated in FIG. 6, a conventional leaf spring 2 of fiber reinforced plastics is provided substantially at its central portion with a position pin 1 which is inserted into a vertical through hole in leaf spring 2 and fixed in place. In use of the leaf spring 2, there will occur concentration of stress at a portion adjacent the through hole because the reinforcement fibers in leaf spring 2 are disconnected by provision of the vertical through hole for position pin 1. As a result, there occur cracks in the upper surface 2a of leaf spring 2 when repeatedly applied with a tension force. To avoid such a problem, as is illustrated in FIG. 7, a seat plate 4 integral with a position pin 3 has been adhered to the central portion of leaf spring 2. It has, however, been observed that such adhesion of the seat plate 4 results in decrease of its fatigue strength against a load acting thereto in a fore-and-aft direction.